During their lifetime, organisms often acquire unwanted foreign or mutated DNA that may negatively affect their health. Traditional modes of diagnosis are often unable to detect the presence of deleterious DNA; additionally, common treatments for such diseases do not address the underlying cause of disease—changes at the level of the genome, and therefore do not discriminate well between target and healthy cells. This lowers the therapeutic efficacy of such conventional treatments. New types of early-detection imaging agents and sequence-specific gene therapies are needed to diagnose and remove unwanted DNA in diseased cells, without affecting healthy, neighboring cells. Imaging and elimination of unwanted genes and gene products have been major goals of molecular biology over the last few decades, and a sudden proliferation of different RNA interference techniques (Gonzalez-Alegre, Pharmacol. Ther. 2007, 114, 34-55; Natt, Curr Opin Mol. Ther. 2007, 9, 242-247; Scherer et al., Gene Ther. 2007, 14, 1057-1064) attest to that trend. As a result of recent advancements in nanotechnology, biologists now have access to materials with novel properties which emerge only at the nano scale, enabling innovative imaging and therapeutic approaches (Roco et al., The Office of Science and Technology. 2007; Rajh et al., J Phys Chem B. 2002, 106, 10543-10552; Rajh et al., Chemical Physics Letters. 2001, 344, 31-39).
Although DNA nanoconjugates may serve as possible vehicles to image and remove unwanted DNA, their targeting efficiency and intracellular retention may be lowered by cellular factors, such as degradation by intracellular nucleases. To address these potential problems and improve the stability of hybridization with target sequences, additional nanoconjugates are needed for diagnostic, clinical, and research applications.